1. Technical Field
The present invention relates to a power transmission device.
2. Description of the Related Art
For example, the related art discloses a reduction gear 910 having a reduction mechanism 908 as shown in FIG. 6. The reduction gear 910 is an orthogonal reduction gear provided with a bevel pinion 914 provided at a leading end of an input shaft 912, and a bevel gear 918 which is provided at an intermediate shaft 916 and is meshed with the bevel pinion 914. The intermediate shaft 916 is further provided with an intermediate pinion 920, and the intermediate pinion 920 is meshed with an output gear 924 provided at an output shaft 922.
The input shaft 912 is supported by a motor-side bearing 926 and a motor-opposite-side bearing 928. The motor-side bearing 926 of the input shaft 912 is accommodated in a bearing casing 930A disposed to protrude from a reduction gear casing 930 (as a portion thereof). In addition, the intermediate shaft 916 is supported by bearing supporting portions 936 and 938 having bearings 932 and 934.
In the reduction gear 910, the motor side of the input shaft 912 protrudes from the bearing casing 930A. A fan (a cooling fan) 940 is mounted on a protruding portion 912A of the input shaft 912.
A fan cover 950 is attached to the fan 940. In this way, by an air flow caused by the fan 940, in particular, the bearing casing 930A of the input shaft 912 is efficiently cooled and the cooling of the entirety of the reduction gear casing 930 is also performed together therewith.